Process of making photographic emulsions



Patented Feb. 4, 1936 PROCESS OF MAKING rno'roonarmo EMULSIONS Max Schmid, Riehen, near Basel, Switzerland, assignor to Society oi. Chemical Industry In ,Basle, Basel, Switzerland No Drawing. Application December s, 1933, Serial No. 701,531. In Switzerland December 4 Glaims.

According to this invention valuable photographic emulsions' are obtained by mixing the components necessary for making an emulsion and subsequently ripening the mixture, and, dur- 5 ing the ripening stage, withdrawing at least two portions of the emulsion of different degrees of ripening and then uniting these portions,

v Emulsions made in this manner have the property that when spread. upon a support they give light-sensitive layers which, whileof good covering power, have a high sensitivity and a remarkable freedom from halation, even without the usual anti-halatlon devices. If the emulsion is made from only two withdrawn portions its properties will be influenced according tothe degree of ripening of each portion; for instance, if the portion of less ripeness prevails there will be obtained an emulsion which is less sensitive to light and shows steeper gradation and stronger covering power; if the portion of greater ripeness prevails the emulsion will. have a high sensitivity and a greater softness.

If the withdrawal of the twoportions of different degrees of ripening is carried out by allowing these portions to flow into a common vessel, there is a simplification in the manufacture with retention of covering power, may be still further increased.

As by grading the degree of ripeness of the;

several portions, whether by raising or lowering the ripening temperature or by prolonging or curtailing the duration of the ripeningror by both thesemethods, the properties of the emu] sion obtained can be profoundly influenced, so

1 also canthe properties, particularly the gradae tion curves, of the finished emulsion be influenced by the ratio in which the portions withdrawn from the ripening mixture are mixed with each other.

For example, if at the beginning of the rise in f sensitivity of the ripening there are withdrawn small portions of the emulsion and then the portions afterwards withdrawn continuously in,

. properties.

(01.95-7) v creased in quantity, the final emulsion obtained will have softer gradations which, according to the mode of working, will not be at fault or only little so'i'n the shadows. If the quantities of the portions of high degree of ripeness are still further increased at the cost of the quantities of the portions or lower degree of ripeness, one can lights. I

If portions of emulsion are progressively withdrawn duringthe period of risingsensitiveness to light, final emulsions are obtained which, when brought on to the supports afford extremely valuable photographic layers. These are characterized by high sensitiveness, remarkable durability and high range of sensitiveness with good gradation. The gradations oi emulsions obtainable in this manner may be influenced within wide limits by the manufacture of the emulsion and may be adapted to the requirements of the photographic material desired.

As already stated, by varying the stages at which the portions of emulsion are withdrawn" from the ripening mass, the properties, forinstance general sensitivity, gradation curves, canb'einfiuenced almost to any extent in. a very simple manner, and this may be, assisted by varying other conditions which influence these Without disadvantageous effect on the emulsions obtained, the increase in sensitivity may be driven by this process up to the beginning of fog.

The present invention may be used for making acid emulsions, ammoniacal emulsions and, it

desired, boiled'emulsions. .By addition of agents which increase sensitivity, the sensitivenessmay be further raised, and by the addition '01 sensitizers color-sensitive layers may. be produced.

Accordingly as the emulsions are compounded and accordingly as theripening is conducted in the present. process, layers canbe obtained for various purposes oi -photography and kinematography, for instance, negative films, plates, diapositive layers, reversal, films, fine-gram layers, layers sensitive .to light for color photography and color kinematography, layers for'light-sound production,,.and developing papers;

These layers serve for making photographic pictures. The negative and positive layers produced by the process may be used alone or in combination with other layers which are obtained from emulsions made by known processes. If as the negative layer there is used one the gamma in accordance with the invention may be used alone or together with other emulsions made according to this process or to *a known process.

The following examples illustrate the invention,

the parts being by weight:-

Example 1 A filtered solution of 1200 parts of silver nitrate, 1100 parts of ammonia (specific gravity 0.91) and 40 parts of citric acid in 6000 parts of water is run, in the course of 20 minutes, into a stirring vessel I containing a solution at a temperature of 28 C. consisting of 6000 parts of we.-

ter, 600 parts of hard gelatine, 1000 parts of potassium bromide, 20 parts of crystallized sodium carbonate, 18 parts of potassium iodide and 200 parts of an alcoholic solution of erythrosine (1:800). The mixture in this vessel I is now heated gradually to 60 C., while at the same time the mixture is what an adjustable speed into an additional gelatine solution containedin a stirring vessel II, kept at 25 C. internal temperatureythe solution consisting of 2000 parts of.

water and 300 parts of soft gelatine. In the stirring vessel I the temperature of 60 C. is maintained for about 50-60 minutes and care is taken, by adjusting the speed of outflow, that after this time, according to the desired gradation, all or the greater part of the mixture in vessel I is run into the vessel 11 cooled to 25 C. When the whole has run out the mixture in vessel 11 is mixed with a solution of 250 parts of mediumand 250 parts of soft gelatine in 1000 parts of water, the whole is stirred for some time longer and the mixture in vessel 11 is allowed to solidify by cooling. The completely solid emulsion is cut up into small pieces and in this form thoroughly washed.

Beiore pouring or spreading this emulsion on the support the pieces aregmelted together in the stirring vessel I at about C. When the whole has melted to a homogeneous emulsion'there are allowed to run, for the purpose of further ripening and if desired with addition of agents that increase sensitiveness, sensitizers or the like, as has been described for the first ripening, portions of the emulsion from the stirring vessel" Iv into a stirring vessel 11 which contains a solution at 25 C. consisting of 2000 parts of water, 10 parts of potassium bromide, 400 parts of soft gelatine, 300 parts of medium gelatine, 500 parts of alcohol and 100 parts of an aqueous solution of 2 per cent. strength bf chrome alum and other additions.

At the beginning of the withdrawal oi, the emulsion from vessel I into vessel II the temperature in vessel I is raised to 50 C. this temperature is maintained until the desired sensitiveness to light has been attained and all the emulsion is in the vessel 11, cooled to 25 C. The

filtered emulsion is applied to the supports and dried as usual.

graphic exposure material of high sensitivity, good covering power and gradation.

By varying the composition of the emulsion by omitting sensitizers or using further sensitizers, and further by varying the ripening process, universal, portrait, dispositive, pan, reversal and other emulsions can be obtained.

Example 2 The solutions necessary for making the emulsion areas follows:-

Parts Solution 1: Water 6000 Silver nitrate 1200 Ammonia (specific gravity 0.91) to which are added 1100 Citric acid dissolved in Water 100 Parts Solution II: Water 6000 Hard gelatine 600 Potassium bromide 1000 Potassium iodide 18 Crystaliized sodium carbonate 20 Erythrosine solution (1:300)- 300 Parts Solution 111: Water 3000 Medium gelatine 250 Soft gelatine 550 Parts Solution IV: Water 2000 Potassium bromide solution of 10 per cent strength--- 10 Soft gelatine 400 Medium gelatine 300 Tarts Solution V: Alcohol 500 Chrome alum solution of 2 per cent strength 100 Tartrazine solution (1:100) 300 I a temperature of 28 C. of the emulsion thus obtained about 6 liters are run into Solution III,

kept at 25 C. The temperature of the mixture of Solutions I and II is now raised to 60 C. and

is maintained thereat for 30 minutes; when 4 liters of the mixture are run into Solution III, kept at 25 C. The rest of this mixture of Solutions I and II is ripened for a further 50 minutes at 60 C. and is then added to Solution IEII.

Solutions I, II and III are now mixed. The mixture is allowed to solidify by cooling and the solidifled emulsion is washed thoroughly with flowing water.

After the washing and draining the comminuted emulsion (noodles) is melted at 40 C.; of this molten emulsion about 10 liters are run into Solution IV and kept at 30 C., the temperature ,of the melted noodles is raised to 50-60 C. and kept thereat for about 10 minutes, whereupon 8 liters thereof are run into Solution IV; the residue is further ripened for about 10 minutes at 50-60 C. and also added to Solution IV.

Solutions I, II, I11 and IV are now mixed together. The mixture is diluted with water to 26 liters and the emulsion allowed to solidify by cooling. The solidified emulsion before it is cast is subdivided into several parts of about the same size as each other. The first part is melted at 50" 0., kept at this temperature for 5 minutes and then the second part of the emulsion is added and the procedure continued until all has been melted. To the completely melted emulsion there is then added Solution V and, after mixing, the whole is cooled to about 33 C. and this emulsion is filtered and cast.

If, according to this invention, portions of emulsion are continuously or intermittently withdrawn from the ripening operation in such a manner that at the beginning of the ripening small portions and towards the end of the ripening large portions are withdrawn, highly sensi-- tlve ortho-chromatic photographic layers having gradation curves of particular technical value are obtained. 1

What I claim is:-

1. Process of making photographic silver halide gelatine emulsions bymixing the components necessary for the preparation or the emulsions and ripening the emulsions, consisting in withdrawing during the ripening of the silver halide geiatine emulsion at least two portions thereof,

of diiierent degrees of ripeness, and then uniting them.

2. Process of making photographic silver halide gelatine emulsions by mixing the components necessary tor-the preparation oi! the emulsions and ripening the emulsions, consisting in withdrawing durlng the ripening of the silver halide gelatine emulsion at least two portions thereof, of diflerent degrees of ripeness, into a common vessel.

3. Process 0! making photographic silver halide gelatlne emulsions by mixing the components necessary for the preparation 01' the emulsions and ripening the emulsions, consisting in withdrawing during the ripening of the silver halide gelatine emulsion several portions thereof, 01' different degrees of ripeness, into a common vessel, the withdrawal of the several portions being efle'cted at short intervals 0! time.

4. Process of making photographic silver halide gelatine emulsions by mixing the components necessary for the preparation of the emulsions and ripening the emulsions, consisting in with.-

drawing during the ripening of the silver halide gelatine emulsion portions thereof, of dliierent degrees of ripeness, into a common vessel, the withdrawal of the portions being continuous. 

